KR20100014263A - Carbon nanofiber, method for producing the same, and use of the same - Google Patents

Abstract

Disclosed is (1) a carbon nanofiber containing not more than 6% by mass of Fe and not more than 3% by mass of V as metal impurities other than carbon, which does not substantially contain a metal element other than Fe and V. Also disclosed is (2) a method for producing such a carbon nanofiber, which is characterized in that a catalyst, which is obtained by loading a carbon carrier with Fe and V, and a carbon-containing compound are brought into contact with each other at a high temperature. Further disclosed are (3) a resin composite body obtained by blending such a carbon nanofiber and (4) use of such a resin composite body. The present invention enables to obtain a low-cost carbon fiber filler containing only a few metal impurities. Only a few amount of this carbon fiber filler enables to exhibit electrical conductivity.

Description

Carbon nanofiber, manufacturing method and use thereof {CARBON NANOFIBER, METHOD FOR PRODUCING THE SAME, AND USE OF THE SAME}

(Cross-reference of related application)

This specification includes all the contents disclosed in the specification, drawings, and the summary of the Japanese application (Japanese Patent Application No. 2007-145255) filed on May 31, 2007.

(Technology)

The present invention relates to carbon nanofibers suitable as a conductive filler, a method for producing the same, and uses thereof.

Background Art Conventionally, it is known to obtain a conductive resin composite material in which conductivity is imparted by blending conductive fillers such as carbon black, carbon fiber or metal powder with matrix resins such as thermosetting resins and thermoplastic resins.

However, in order to impart high conductivity (especially volume resistivity of 1 × 10 ⁶ Ω · cm or less) to this kind of composite material, it is necessary to add a substantial amount of conductive filler. However, there is a drawback that it adversely affects the physical properties of the matrix resin so that the original properties of the resin are not reflected in the prepared composite material.

Therefore, the filler material which can express electroconductivity high enough even with a small compounding quantity was desired.

Japanese Patent Application Laid-Open No. 2004-360099 (Patent Document 1) discloses a fishbone-type carbonaceous microfibrous body which is excellent in kneading with resin and excellent in conductivity as such a conductive filler material.

The fishbone carbon fiber refers to a structure in which the graphite mesh plane is inclined with respect to the fiber axis, but in addition to that, the graphite mesh plane is almost perpendicular to the fiber axis, and carbon fibers which are not hollow are also known. The term nanofibers is commonly used.

On the other hand, carbon nanotubes having a structure in which graphite mesh planes are substantially parallel to the fiber axis have been widely studied.

As a method of producing such carbon nanofibers, a method by a chemical vapor deposition method (hereinafter referred to as a CVD method) is known, and a method of supporting and using a catalyst metal on a carrier and an organic metal complex without a carrier are used as catalysts. It is known to produce catalyst metals in the gas phase in the reaction system.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-360099

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-292227

Patent Document 3: Japanese Patent Publication No. 2006-502953

Patent Document 4: Japanese Patent Application Laid-Open No. 2004-26626

Non-Patent Document 1: Applied Catalysis A: 283 (2005) 137

Non-Patent Document 2: Chemical Physics Letters 374 (2003) 22-228

The carbon fibers shown in Japanese Patent Application Laid-Open No. 2004-360099 (Patent Document 1) have many residues of catalyst components when calculated from the examples described in the publication. When the amount of impurities in the resin composite material is large in this way, there is a problem that the mechanical properties of the composite material, including strength, are significantly lowered because the impurities promote decomposition of the resin during molding.

In the above CVD method, the latter organic metal complex or the like is used as a catalyst, and there are many defects in the graphite layer, and if it is added as an electrically conductive filler without conducting heat treatment at a high temperature, the conductivity may not be expressed. It was difficult to manufacture. The method of using the former catalyst carrier can be broadly divided into (i) a method of using a substrate as a carrier and (ii) a method of using a powdery carrier. The method of using the substrate of (i) is widely used in the laboratory level research because the size of the catalyst metal can be controlled by applying various film forming techniques. For example, in Chemical Physics Letters 374 (2003) 22-228 (Non-Patent Document 2), a fiber diameter of about 10 to 20 nm is formed by using a substrate on which a 10 nm aluminum film, a 1 nm iron film, and a 0.2 nm molybdenum film are formed on a silicon substrate. It is disclosed that a multilayer tube having a tube shape and a two-layer nanotube are obtained. In order to use the carbon nanotubes obtained by this method as a resin composite material, it is necessary to separate them from the substrate and recover them as carbon nanotubes. The carbon nanotubes recovered in this way substantially contain only the catalyst metal component as impurities, but the production efficiency of the carbon nanotubes is poor, and therefore, the catalyst metal component is often left in a large amount. In addition, if the method is to be used industrially, the surface area of the substrate cannot be secured without a large number of substrates arranged, so that the device efficiency is low, and the support of the catalyst metal on the substrate, the synthesis of carbon nanotubes, and the Since many processes such as recovery are necessary, it is not economical and has not been put to practical use.

On the other hand, in the method using the powder carrier, the specific surface area is larger than the method using the substrate, so that the device efficiency is high and the reaction apparatus used for various chemical synthesis can be used. It has the advantage that not only the production method on the premise but also the continuous reaction is possible. However, in this method, it is difficult to obtain a high-purity carbon fiber because the catalyst carrier is incorporated into the product from the characteristics of the synthesis method.

Therefore, as a method of reducing the amount of these impurities, (1) a method of heat treatment at a high temperature, (2) a method of washing and removing with an acid or an alkali, and the like are known, but all of the methods are not economical because the process is complicated. In particular, the catalyst carrier and the catalyst metal in the carbon nanotubes are often covered with a carbon film when they are washed away with an acid or an alkali, so that the carbon film is removed by using an acid such as nitric acid with oxidation power or by partial oxidation. Otherwise, complete impurity removal is often difficult. However, when such an oxidizing acid is used, not only the carbon coating on the surface of the carrier and the catalyst but also the carbon nanotubes themselves may be damaged or deteriorated, which may result in deterioration of conductivity or strength.

As a method of reducing impurities derived from a catalyst carrier, it is known to use carbon such as commercially available graphite or activated carbon as a carrier (for example, Japanese Patent Laid-Open No. 2004-292227; Patent Document 2). However, in this case, since the carbon production amount is small, impurities derived from the catalyst metal increase, and high purity carbon fibers are not obtained.

Therefore, in order to improve the carbon fiber production amount, a method of oxidizing a carbon carrier using hydrogen peroxide or nitric acid in advance is disclosed (Applied Catalysis A: 283 (2005) 137; Non-Patent Document 1). However, even in this case, the process is complicated and not economical, and it cannot be said that the reduction of impurities is also sufficient.

In addition, Japanese Patent Publication No. 2006-502853 (Patent Document 3; WO2004 / 035882) discloses that carbon nanofibers having a carbon content of 95% by mass or more can be obtained by using a special carbon black having a total oxygen content of 10% by mass or more as a carrier. . However, when the present inventors added the filler prepared using such a special carbon carrier to a resin composite material as shown in the comparative example mentioned later, sufficient electroconductivity is not expressed.

In addition, elements such as iron, nickel, and cobalt are generally used as catalysts to improve the amount of carbon fiber produced, but other methods of adding other fiber metals as promoters have also been studied (for example, Japanese Patent Laid-Open). 2004-26626; Patent Document 4, etc.).

However, the combination of the main catalyst, the cocatalyst, the catalyst carrier, the hydrocarbon used as the carbon source, and the production efficiency of the carbon fiber and the properties as the filler are greatly changed by the reaction conditions. Is the current situation.

That is, until now, it is substantially free of metal elements (that is, metal elements other than Fe and V) as impurities, and it is possible to express conductivity by adding a small amount in the resin composite, and no cheap carbon fiber filler exists.

Accordingly, an object of the present invention is to provide an inexpensive carbon fiber filler material which can express conductivity with a small amount of addition without substantially including metal elements (metal elements other than Fe and V) as impurities.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, the present inventors discovered carbon nanofibers as a high performance electroconductive filler, and its manufacturing method, and came to complete this invention.

That is, this invention relates to the following carbon nanofibers, its manufacturing method, and use, for example.

1. Carbon nanofibers containing 6 mass% or less of iron (Fe) and 3 mass% or less of vanadium (V) as metal elements other than carbon, and substantially free of metal elements other than Fe and V. .

2. A method for producing carbon nanofibers, comprising contacting a catalyst carrying Fe and V on a carbon carrier with a carbon-containing compound at 400 to 1100 ° C.

3. The method for producing carbon nanofibers according to 2 above, wherein the specific surface area of the carbon carrier is 30 to 500 m 2 / g.

4. The method for producing carbon nanofiber according to the above 2, wherein the carbon carrier is obtained by heat-treating carbon black having a specific surface area of at least 500 m 2 / g at 2000 to 3000 ° C.

5. The carbon nanofibers using the catalyst according to the above 2, wherein the iron concentration in the catalyst is 5 to 30% by mass as calculated by {(iron mass) / (iron mass + carrier mass)} × 100 (mass%). Manufacturing method.

6. The method for producing carbon nanofiber according to the above 2, wherein the vanadium concentration in the catalyst is 20 to 100 mol% based on the number of moles of iron.

7. The method for producing carbon nanofiber according to the above 2, wherein the carbon-containing compound is at least one selected from CO, CO ₂ , aliphatic hydrocarbons and aromatic hydrocarbons.

8. The method for producing carbon nanofiber according to the above 2, wherein the carbon-containing compound is ethylene.

9. The method for producing carbon nanofibers according to the above 2, wherein a carrier gas is used in addition to the carbon-containing compound.

10. The method for producing carbon nanofiber according to 9 above, wherein the carrier gas is a gas containing hydrogen.

11. Carbon nanofiber obtained by the method in any one of said 2-10.

12. A carbon nanofiber-resin composite formed by blending the carbon nanofibers according to 1 or 11 above with a resin.

13. An electrical / electronic parts container using the carbon nanofiber / resin composite according to 12 above.

14. A member for conductive sliding using the carbon nanofiber resin composition as described in 12 above.

15. A conductive thermally conductive member using the carbon nanofiber / resin composite according to 12 above.

(Effects of the Invention)

According to the present invention, carbon nanofibers suitable as fillers for conductive resins are obtained. Since the carbon nanofibers in the preferred embodiment of the present invention can impart higher conductivity to the resin with a smaller amount of addition than before, the conductive resin composite material having a small amount of impurity metal elements can be obtained at low cost.

1 is a photograph of the product obtained in Example 1 observed with a transmission electron microscope (TEM).

2 is a photograph of the catalyst portion in the product obtained in Example 1 observed with a transmission electron microscope (TEM).

In the carbon nanofibers in the preferred embodiment of the present invention, the graphite plane is inclined with respect to the fiber axis. The angle θ formed between the fiber axis and the graphite plane is measured from the transmission electron microscope (TEM) image (see FIG. 1). Although it does not specifically limit about angle (theta), 15-90 degree is preferable and 30-70 degree is more preferable.

In this way, the graphite plane is inclined with respect to the fiber axis, so that many active points are present on the surface thereof compared with tubular fibers having θ of almost 0 degrees. In addition, the adhesion is expected to be improved, the dispersibility is improved, or the interface strength with the resin is improved. As a result, in the case of a composite material, even a small amount of addition can be expected to improve the characteristics sufficiently, so it is economical.

The fiber center part may be hollow, may be connected here and there, or it may be connected as a whole and may not have a hollow part.

In the carbon nanofibers, 6 mass% or less of iron as a metal element, preferably 3 mass% or less, more preferably 1 mass% or less and 3 mass% or less, preferably 2 mass% or less, more preferably Is characterized in that it contains substantially no metal element (ie, a metal element other than Fe and V) as other impurities except that it contains 1 mass% or less. The metal element herein refers to all elements except H, N, O, S, F, Cl, Br, I, He, Ne, Ar, Kr, Xe, Rn and carbon in the periodic table.

In a preferred embodiment of the present invention, a powdery catalyst in which Fe and V are supported as a metal catalyst on a specific powdery carbon carrier as described below is used. The produced carbon fiber may contain a carbon carrier in addition to the metal elements of iron and vanadium.

When carbon nanofibers are added to the resin as a filler, depending on the type of resin and the molding method, the carbon nanofibers may be exposed at high temperatures during kneading, molding, or curing with the resin. Deterioration, poor curing, etc. may occur. In addition, since the residual metal impurities reduce the strength and properties over time or elute the metal impurities as ionic impurities when using the molded product, it is desired that the impurities in the carbon nanofibers be suppressed to be extremely low. have.

On the other hand, since the carbon carrier has a small amount of residual or similar characteristics to the carbon fibers produced, the carbon carrier hardly has the same effect as other metal elements.

The method for analyzing metal elements is not particularly limited, but preferably ICP-AES (inductively coupled plasma-atomic emission analysis) analysis is employed. Although the pretreatment method of a sample is not specifically limited, What is necessary is just to melt | dissolve further adding phosphoric acid to what decomposed | disassembled carbon nanofibers into sulfuric acid and nitric acid. In addition, substantially free of other metal elements usually means less than 100 ppm.

[Synthesis method of carbon nano fiber]

catalyst:

It is preferable to use iron as a main catalyst, vanadium as a cocatalyst element, and carbon as a carrier.

The method of supporting iron and vanadium on the carbon carrier is not particularly limited. For example, a metal oxide or salt can be supported on a carrier by impregnating the carrier in a non-aqueous solution in which a salt of iron or vanadium is dissolved (for example, a methanol solution) or by an aqueous dispersion, followed by sufficient dispersion and drying. Alternatively, the solution may be impregnated with iron and vanadium, respectively. A precipitate may be formed from a solution containing iron or vanadium and deposited on a carrier.

Although the iron raw material used here is not specifically limited, Since it is easy to prepare the metal salt solution used by the method mentioned above, mineral salts, such as iron nitrate, iron nitrate, iron sulfate, alum, and acetylacetonate complexes, iron chlorides, bromination Halides, such as iron and iron fluoride, and organic acid salts, such as iron oxalate and iron stearate, are used suitably.

Although the vanadium raw material used here is not specifically limited, Oxide salts, such as vanadate, vanadil salt, chlorides, such as vanadium chloride, oxides, such as vanadium oxide, and acetyl from the ease and cost of preparation of the metal salt solution used by the method mentioned above. Complex salts such as acetonate complex analogs and the like are suitably used.

It is preferable that the specific surface area is 30-500 m <2> / g, as for an example suitable as a carbon carrier, It is more preferable that it is 60-500 m <2> / g, It is most preferable that it is 100-300 m <2> / g. It is preferable to use a large specific surface area because the amount of iron can be finely supported and a large amount can be increased. However, when the specific surface area is too large, the electrical conductivity when the resin composite material is used tends to be lowered.

Moreover, it is preferable to have a surface of graphite, for example as another preferable carbon carrier. Carbon carriers having a graphite surface having a high oxygen content and having less surface functional groups than carbon carriers having surface functional groups are preferable.

As a specific example, carbon materials such as carbon black having a high specific surface area or carbon materials are heat-treated at 2000 to 3000 ° C. in an inert gas, and cutting residues of graphite electrodes are preferred, and carbon black having a specific surface area of 500 m 2 / g or more is preferably used. Most preferably, heat treated at 2000 to 3000 ° C. Here, carbon black is used as a generic term for particulate carbon powders and aggregates thereof, such as those obtained by pyrolysis methods such as acetylene method and thermal method, those obtained by incomplete combustion method using furnace black as a representative example, and ketjen black.

Conventionally, it was mainly to use a highly active carrier having a very large specific surface area such as activated carbon, or generally a highly active carrier having modified the surface thereof. In the present invention, it is possible to use a carbon carrier having a low surface activity and having a medium specific surface area or a carrier having a graphite surface having almost no surface functional groups. In the case of using a carrier having such a low activity, the production of carbon fibers is generally poor. However, in the present invention, the catalyst activity has been improved by selecting any specific catalytic metal component such as Fe and V.

In the case of using a conventional high active carbon carrier, carbon nanofibers produced by carbon nanofibers may be impurity such as carbon particles or amorphous to the fiber surface or between fibers. When carbon deposition is likely to occur and used as a resin filler, it is often necessary to increase the amount of filler added in order to obtain desired characteristics whether the dispersibility is poor or the characteristics of the fiber itself are low.

In a preferred embodiment of the present invention, it is also possible to prevent the deterioration of the function of carbon nanofibers and carbon nanofibers-containing materials caused by such by-product carbon species by using a carrier having a very low activity.

In addition, when the catalyst adjustment method of the present invention is used, the catalyst metal is often present as a metal salt, a complex, or an oxide of the precursor prior to the start of the reaction. Thus, the catalyst metal is generally subjected to a reduction treatment or the like before the start of the reaction. After the reduction, the reaction with the hydrocarbon is started. By the way, the carbon carrier having the activated carbon surface as used in the prior art is a catalyst precursor and the like is often reduced by the reduction action of the carbon itself, so even if the reduction to the catalyst metal occurs even if not specifically intentional reduction treatment There is. Therefore, carbon fiber can be produced from fine metal catalyst particles by combining an appropriate carbon source and reaction conditions.

On the other hand, the size of the catalyst metal particles may significantly affect the production mechanism of the carbon fibers to be produced. In the fine catalyst metal particles, tubular carbon nanotubes having the above-described θ of almost 0 degrees are likely to be produced, and from the larger catalyst metal particles, fibers in which the graphite layer is inclined with respect to the fiber axis or vertical fibers are likely to be produced. In addition, depending on the combination of the carbon source and the reaction conditions, the reduction of the metal catalyst particles may occur in a region lower than the reaction temperature, and in this case, the aggregated growth between the highly active metal catalyst particles proceeds too much to generate carbon nanofibers. There was a tendency that it did not function as a catalyst and little carbon content was produced or only carbon other than fibers such as amorphous carbon was produced.

Therefore, when the carbon carrier having the activated carbon surface as described above is used, carbon fibers are often produced from the fine metal catalyst particles, and thus, tubular fibers are often produced. Carbon nanofibers in which the graphite layer is inclined with respect to the fiber axis, which is a preferred embodiment of the present invention, has a higher interaction with the resin when used as a filler material as compared with such a tube-type carbon fiber to improve the physical properties of the resin. It is possible.

As described above, in the present invention, since the size of the catalyst metal particles is appropriately adjusted by adding vanadium and selecting an appropriate carbon carrier, it is estimated that fibers inclined with respect to the fiber axis tend to be produced as a result.

In the present invention, the iron concentration in the catalyst for producing carbon nanofibers is 5% by mass or more, as calculated by {(iron mass) / (iron mass + carrier mass)} × 100 (mass%), preferably 5 It is -30 mass%, and 5-20 mass% is the most preferable. If the iron concentration is less than 5% by mass, the yield tends to be very low. On the other hand, even if the iron concentration is too high, there is a limit not to increase the quantity indefinitely, but there is a tendency to increase the impurity concentration in the product.

A suitable amount of vanadium is 20 to 100 mol%, preferably 20 to 80 mol%, and most preferably 40 to 80 mol% with respect to the amount of iron substance. When the addition amount of vanadium is lower than 20 mol%, there exists a tendency for the electrical conductivity at the time of adding to resin to fall. If it is higher than 100 mol%, the amount of carbon nanofibers tends to decrease.

[Carbon-containing compound]

In this invention, a carbon containing compound is not specifically limited. As a carbon compound is _{CCl 4, CHCl 3, CH 2} Cl 2, CH 3 Cl, CO, CO 2, CS 2 and so on in addition to the first half of organic compounds can be used. Examples of particularly useful compounds include higher the CO, CO _2, aliphatic hydrocarbons and aromatic hydrocarbons. In addition to these, carbon compounds containing elements such as nitrogen, phosphorus, oxygen, sulfur, fluorine, chlorine, bromine and iodine can also be used.

Examples of preferred carbon compounds are CO, CO ₂ Inorganic gases such as, alkanes such as methane, ethane, propane, butane, pentane, hexane, heptane and octane, alkenes such as ethylene, propylene and butadiene, alkynes such as acetylene, benzene, toluene, xylene and styrene Polycyclic compounds having a condensed ring such as monocyclic aromatic hydrocarbon, indene, naphthalene, anthracene, phenanthrene, cycloparaffins such as cyclopropane, cyclopentane, cyclohexane, cyclopentene, cyclohexene, cyclopentadiene, dicyclopenta Cycloolefins such as dienes, and alicyclic hydrocarbon compounds having condensed rings such as steroids. Furthermore, derivatives containing oxygen, nitrogen, sulfur, phosphorus, halogen, and the like in these hydrocarbons, such as oxygen-containing compounds such as methanol, ethanol, propanol, butanol, sulfur-containing aliphatic such as methyl thiol, methyl ethyl sulfide, and dimethyl thioketone Sulfur-containing aromatic compounds such as compounds, phenylthiol, diphenyl sulfide, sulfur-containing or nitrogen-containing heterocyclic compounds such as pyridine, quinoline, benzothiophene and thiophene, halogenated compounds such as chloroform, carbon tetrachloride, chloroethane and trichloroethylene Natural gas, gasoline, kerosene, heavy oil, creosote oil, kerosene, terepin oil, camphor oil, pine root oil, gear oil, cylinder oil, etc. may also be used. It is also possible to use mixtures of these.

Further preferred carbon compounds include CO, methane, ethane, propane, butane, ethylene, propylene, butadiene, acetylene, benzene, toluene, xylene and mixtures thereof.

[Carrier gas]

In the production of the carbon nanofibers of the present invention, it is recommended to use a carrier gas in addition to these carbon compounds. As the carrier gas, hydrogen, nitrogen, carbon dioxide, helium, argon, krypton, or a mixed gas thereof can be used. However, gases containing oxygen molecules such as air (ie, molecular oxygen: O ₂ ) are not suitable. The catalyst precursor compound used in the present invention may be in an oxidized state, and in this case, it is preferable to use a gas containing hydrogen as the carrier gas. Therefore, as a preferable carrier gas, it is a gas containing 1 volume% or more of hydrogen, 30 volume% or more, most preferably 85 volume% or more, for example, 100 volume% hydrogen and the gas which diluted hydrogen with nitrogen.

In this invention, it is preferable to perform a reduction process before supplying a carbon containing gas. The reduction treatment is realized by holding in reducing gas such as hydrogen.

The temperature and time for the reduction treatment are not determined uniformly because they depend on the type of carrier used, the contact efficiency with the reducing gas, the type of the reducing gas, etc., but the reduction temperature is 300 to 1000 ° C and the reduction time is 10 minutes to 5 hours is good, and in the case of reduction at low temperature, it is better to take long reduction time. Moreover, preferable reduction temperature is 500-700 degreeC, and reduction time is 10-60 minutes.

In this reduction treatment, the catalytic metal particles may not be able to maintain an appropriate size even if the reduction is excessive even if the reduction is excessive. The size of the preferred metal catalyst particles can be obtained by observing the size of the metal particles remaining in the tip portion of the produced fiber by TEM image or the like (see FIG. 2). Generally, about 5-100 nm is preferable, about 5-50 nm is more preferable, and 10-40 nm is optimal.

[Carbon-containing gas concentration]

It is preferable to introduce a carbon-containing compound mentioned above after heating and vaporizing a liquid and solid thing at normal temperature. Since the supply amount of these carbon-containing gases differs depending on the catalyst used, the carbon source, and the reaction conditions, it is not uniquely determined. However, the preferred range is generally {(carbon-containing gas flow rate) / (carrier gas flow rate + carbon-containing gas flow rate) } X 100 is 10-90 volume%, and 30-70 volume% is more preferable. Especially when the carbon content is ethylene, the range of 30-90 volume% is the most preferable.

In the present invention, the temperature at the time of contacting the catalyst with the carbon-containing compound in order to produce the carbon nanofibers varies depending on the carbon source used and the like, but is generally 400 to 1100 ° C, preferably 500 to 800 ° C. When ethylene is a raw material, it is 400-800 degreeC, 500-640 degreeC is preferable and 520-600 degreeC is the most preferable. If the temperature is too low or too high, the amount produced may be significantly lower. In addition, at a high temperature where generation other than carbon nanofibers occurs, non-conductive materials tend to adhere to the surface of the carbon fiber, which may not be suitable for the application of carbon nanofibers to resin applications.

Carbon nanofibers (hereinafter sometimes referred to only as "carbon fibers") in a preferred embodiment of the present invention exhibit sufficient electrical conductivity when used as a filler even without performing a graphitization step at a high temperature. It is characteristic. Naturally, it is also possible to further improve the electrical conductivity by performing the graphitization treatment at a high temperature.

The carbon fiber in a preferred embodiment of the present invention can be blended and kneaded with a resin to prepare a resin compound. As addition amount of the carbon fiber used for a resin compound, 1-30 mass% is preferable. If the amount is less than 1% by mass, it is difficult to make a sufficient conductive and thermally conductive path in the resin compound. On the other hand, when the addition amount exceeds 30% by mass, it is easy to lose the characteristics of the resin itself.

Although the resin used for the resin composite in preferable embodiment of this invention is not specifically limited, A thermosetting resin, a photocurable resin, or a thermoplastic resin is preferable.

As the thermosetting resin, for example, polyamide, polyether, polyimide, polysulfone, epoxy resin, unsaturated polyester resin, phenol resin and the like can be used. As the thermoplastic resin, for example, nylon resin, polyethylene resin, polyamide resin, polyester Resins, polycarbonate resins, polyarylate resins and the like can be used.

The resin composite containing the carbon fiber in the preferred embodiment of the present invention is a product which requires impact resistance as well as conductivity or antistatic property, such as OA equipment, electronic devices, conductive packaging parts, conductive sliding members, and conductive thermal conductivity. It can be used suitably as a molding material for a member, an antistatic packaging part, and an automobile part to which electrostatic coating is applied. When manufacturing these products, it can follow the shaping | molding method of the conductive resin composition conventionally known. Examples of the molding method include injection molding method, blow molding method, extrusion molding method, sheet molding method, thermoforming method, rotational molding method, lamination molding method, transfer molding method and the like.

Further, the carbon fiber according to the present invention can also be utilized as an additive to an electrode material for a battery or a capacitor and a carrier for various catalysts.

(Example)

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, the following Example is shown for the illustration and does not interpret this invention in any meaning limitedly.

[reagent]

The reagent used in the following examples is as follows.

Iron nitrate hexahydrate (special reagent of JUNSEI CHEMICAL Co., LTD.), Ammonium metavanadate (special reagent from KANTO CHEMICAL Co., Inc.), ammonium tungstate para hydrate (WAKO PURE CHEMICAL INDUSTRIES, LTD. Product), chromium nitrate hexahydrate (product of WAKO PURE CHEMICAL INDUSTRIES, LTD.), Ammonium molybdate (product of WAKO PURE CHEMICAL INDUSTRIES, LTD.), Carbon black show black MAF (product of Cabot Japan KK), carbon black BP- 2000 (product of Cabot Japan KK), carbon black # 3050 (product of Mitsubishi Chemical Corporation), Ketjen black EC-300J (product of KETJEN BLACK INTERNATIONAL COMPANY), UF-G5 (product of SHOWA DENKO KK), VGCF (registered trademark; SHOWA DENKO KK) Product), activated carbon Darko G60 (reagent of WAKO PURE CHEMICAL INDUSTRIES, LTD.), Denka black (product of DENKI KAGAKU KOGYO KABUSHIKI KAISHA), methanol (special reagent of JUNSEI CHEMICAL Co., LTD. Product).

[Heat Treatment of Catalyst Carrier]

A predetermined amount of carbon material was charged into a graphite crucible and heat-treated at 2800 ° C. for 30 minutes in argon gas. The obtained sample was cracked and used for catalyst preparation.

[Preparation of Catalyst]

A predetermined amount of iron nitrate hexahydrate was dissolved in methanol, and a predetermined amount of ammonium metavanadate was dissolved. This was dripped on the support, it knead | mixed, and the paste was obtained. The catalyst was obtained by pulverizing this at 100 degreeC and drying under reduced pressure for 4 hours.

In addition, the predetermined amount (addition amount) of iron nitrate here is computed so that it may be {(iron mass) / (iron mass + carrier mass) x 100 = iron mass% with respect to a carrier mass, and the predetermined amount of ammonium metavanadate (Addition amount) calculates a required amount from the said iron mass and mole number.

[Synthesis of Carbon Nanofibers]

A horizontal reactor of about 40 cm was installed in the center of a 3.2 cm inner diameter quartz tube (1 m in length), 10 quartz boats (2 cm wide) carrying a catalyst were installed and nitrogen was passed through at 500 ml / min. A quartz tube was installed in an electric furnace, and the center temperature was heated to predetermined temperature over 1 hour. Then, it kept at predetermined temperature for 30 minutes. Thereafter, the gas was switched to 500 ml / min of hydrogen and held for another 30 minutes. The gas was then switched to 250 ml / min ethylene and 250 ml / min hydrogen (if 50 vol% ethylene concentration), and after holding for some time the gas was further switched to 500 ml / min hydrogen and cooled to room temperature.

[Creation of Thermosetting Resin Composite]

2g carbon nanofiber and SHOWA HIGHPOLYMER Co., LTD. Weigh 50g of the total epoxy resin B-806 and 2.5g of benzoyl peroxide (35% by weight mixture) from SIGMA-ALDRICH Japan KK with SHINKY MIXERS (trade name) from SHINKY, and mix in stirring mode (2000 rpm) for 3 minutes. And mixing for 3 minutes in degassing mode (2200 rpm). The obtained mixture was placed in a stainless steel die (100 × 100 × 2 mm thick), and cured in an oven at 150 ° C. for 3 hours to obtain a flat carbon nanofiber-containing thermosetting resin composite.

[Measurement of Surface Resistance]

Surface resistivity was measured using a resistivity meter Loresta GP (low resistivity) and Hiresta UP (high resistivity) from MITSUBISHI CHEMICAL Corporation.

Example 1:

 Ethylene was reacted at 540 ° C. for 1 hour using ethylene as a raw material using a catalyst in which Ketjenblack EC-300J was heat-treated at 2800 ° C. with 20% by mass of iron and 80 mol% of vanadium relative to iron. The obtained product was observed by TEM to obtain a carbon nanofiber having a herringbone structure having a diameter of 20 to 50 nm (see FIGS. 1 and 2). As a result of analysis by ICP-AES, Fe: 0.7 mass% and V: 0.3 mass% were detected, but metal elements other than Fe and V were less than 100 ppm.

The resin composite material containing 4 mass% of carbon nanofibers was created using the obtained carbon fiber and thermosetting resin (Repoxy Resin B-806 by SHOWA HIGHPOLYMER Co., LTD.). The characteristic (surface resistance value) of the obtained resin composite material was 3 * 10 <^5> ohm / g (refer Table 1). The electroconductivity was expressed by addition of a small amount of carbon nanofibers of 4 mass%.

Comparative Examples 1-3:

It carried out similarly to Example 1 except having used molybdenum (ammonium molybdate), chromium (chromium nitrate), and tungsten (ammonium tungstate) instead of vanadium. The results are shown in Table 2.

As is apparent from Table 2, the conductivity similar to that of Example 1 was not expressed in the graphitized product of Ketjenblack EC-300J carrying Fe-Mo, Fe-Cr, and Fe-W.

Examples 2-7 and Comparative Examples 4-5:

Table 3 as a carbon carrier (Example 2: Carbon black Show black MAF (product of Cabot Japan KK), Example 3: Denka black (product of DENKI KAGAKU KOGYO KABUSHIKI KAISHA), Example 4: Carbon black BP-) 2800 ° C. heat-treated product of 2000 (CABOT JAPAN KK), Example 5: 2800 ° C. heat-treated product of Ketjen Black EC-300J (product of KETJEN BLACK INTERNATIONAL COMPANY), Example 6: UF-G5 (manufactured by SHOWA DENKO KK, 3000 ° C.) High-quality crude graphite powder obtained by heat treatment at), Example 7: VGCF (registered trademark; manufactured by SHOWA DENKO KK, graphite product by heat treatment at 2800 ° C), Comparative Example 4: Ketjen Black EC-300J (product by KETJEN BLACK INTERNATIONAL COMPANY), and Comparative Example 5: Carbon nanofibers were synthesized in the same manner as in Example 1, except that activated carbon Darko G60 (a reagent from WAKO PURE CHEMICAL INDUSTRIES, LTD.) Was used, and thermosetting resin composites were prepared using these properties (surfaces). Resistance). The results are shown in Table 3.

A resin composite material having high purity and high electrical conductivity was obtained by using a carrier having a specific specific surface area (13 to 190 m 2 / g) or a material subjected to heat treatment at 2800 ° C. (Examples 4 to 7). On the other hand, when the specific surface area of the support was too large, the electrical conductivity decreased (Comparative Examples 4 to 5).

In addition, the specific surface area of the catalyst carrier described in these tables | surfaces is the value measured after vacuum degassing at 300 degreeC for 20 minutes using the BET specific surface area measuring apparatus (NOVA1200 by a Yuasa ionics inc. Product).

Comparative Example 6:

In the same manner as in Example 1 in JP 2006-502953 A (Patent Document 3), a catalyst carrying Fe and Ni was prepared by using carbon black # 3050 (manufactured by MITSUBISHI CHEMICAL Corporation) as a carrier. The results show that the electrical conductivity is lowered as shown in Table 3.

Examples 8-10 and Comparative Examples 7-8:

Carbon nanofibers were synthesized in the same manner as in Example 2 using a catalyst in which Fe and V were supported on carbon black, show black and MAF (product of Cabot Japan KK) except that the reaction temperature was 440 to 690 ° C., and the thermosetting resin composite material Was prepared, the characteristic (surface resistance) was evaluated, and the result was shown in Table 4.

In the reaction using ethylene as a carbon source, almost no carbon nanofibers were formed at the reaction temperature of 440 ° C. In addition, when the reaction temperature became a high temperature, the electrical conductivity decreased (690 ° C; Comparative Example 8).

Examples 11-13 and Comparative Examples 9-10:

Carbon nanofibers were synthesized in the same manner as in Example 2 except that the ethylene concentration was changed to 10 to 98% by volume, and a thermosetting resin composite material was prepared to evaluate its properties (surface resistance). The results are shown in Table 5.

When the ethylene concentration is 30 to 90% by volume, the thermosetting resin composite exhibited high conductivity of 7 × 10 ³ to 2 × 10 ⁵ Ω / □, but the electric conductivity was lowered at 10% and 98% by volume outside this range. (Comparative Examples 9-10).

Examples 14-17 and Comparative Example 11:

Carbon nanofibers were synthesized in the same manner as in Example 2 except that a catalyst having an iron loading of 1 to 40% by mass was prepared, and a thermosetting resin composite was prepared to evaluate its properties (surface resistance). The results are shown in Table 6.

In the case of using a catalyst having an iron loading of 5 to 40% by mass, a high conductivity of 4 × 10 ³ to 8 × 10 ⁵ Ω / □ was obtained, but the electrical conductivity was lowered at a loading of 1% by volume (Comparative Example 11 : 5 x 10 ⁹ Ω / □).

Examples 18-21 and Comparative Examples 12-13:

Carbon nanofibers were synthesized in the same manner as in Example 15 except that a catalyst having a vanadium added amount of 10 to 150 mol% based on iron was prepared, and a thermosetting resin composite was prepared to evaluate its properties (surface resistance). The results are shown in Table 7.

When the amount of vanadium added to iron was 20 to 100 mol%, the surface resistance of the thermosetting resin composite showed a conductivity of 3 × 10 ³ to 10 ⁵ Ω / □, but 10 mol% outside of this range (Comparative Example 12) and 150 mol% (Comparative Example 13) showed low electrical conductivity.

Claims (15)

A carbon nanofiber comprising 6 mass% or less of iron (Fe) and 3 mass% or less of vanadium (V) as metal elements other than carbon, and substantially free of metal elements other than Fe and V. A method for producing carbon nanofibers, comprising contacting a catalyst carrying Fe and V with a carbon support and a carbon-containing compound at 400 to 1100 ° C. The method of claim 2, The specific surface area of the carbon carrier is a method for producing carbon nanofibers, characterized in that 30 ~ 500㎡ / g. The method of claim 2, The carbon carrier is a carbon nanofiber manufacturing method, characterized in that the heat treatment of carbon black with a specific surface area of more than 500㎡ / g at 2000 ~ 3000 ℃. The method of claim 2, The production of carbon nanofibers is characterized in that the iron concentration in the catalyst is used in the range of 5 to 30 mass% as calculated by {(iron mass) / (iron mass + carrier mass)} × 100 (mass%). Way. The method of claim 2, The vanadium concentration in the catalyst is a method for producing carbon nanofibers, characterized in that using a catalyst of 20 to 100 mol% based on the number of moles of iron. The method of claim 2, The carbon-containing compound is a method for producing carbon nanofibers, characterized in that at least one selected from CO, CO ₂ , aliphatic hydrocarbons and aromatic hydrocarbons. The method of claim 2, The carbon-containing compound is a method for producing carbon nanofibers, characterized in that ethylene. The method of claim 2, A method for producing carbon nanofibers, characterized in that a carrier gas is used in addition to the carbon-containing compound. The method of claim 9, The carrier gas is a method for producing carbon nanofibers, characterized in that the gas containing hydrogen. The carbon nanofiber obtained by the method as described in any one of Claims 2-10. A carbon nanofiber-resin composite comprising the carbon nanofibers according to claim 1 or 11 in a resin. An electric and electronic parts container comprising the carbon nanofiber and resin composite according to claim 12. The carbon nanofiber-resin composite of Claim 12 was used, The conductive sliding member characterized by the above-mentioned. The carbon nanofiber-resin composite of Claim 12 was used, The electroconductive heat conductive member characterized by the above-mentioned.

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